Method and control device for reversing the direction of rotation in a drive train of a working machine

Abstract

Method for reversing the direction of rotation in a drive train (1) of a machine, wherein the drive train has a reversing gear (3) with directional clutches (6, 7), wherein to reverse the direction of rotation one of the directional clutches (6) is opened and the other directional clutch (7) is closed, characterized in that, depending on a temperature difference (ΔT) between an expected temperature (Terw) of the directional clutch (7) to be closed during frictional engagement and a predetermined limit temperature (Tlimit), an energy input into the directional clutch (7) to be closed is controlled by the change of direction such that the temperature (T) of the directional clutch to be closed does not exceed the limit temperature (Tlimit), characterized by the steps S1: Determining an actual temperature (Tist) of the directional clutch (7) to be closed,S2: Determining the expected temperature (Terw) of the directional clutch (7) to be closed upon frictional engagement, based on the determined actual temperature (Tist) and a predicted temperature increase (Terh) due to a predetermined driving strategy during reversal of the direction of rotation; S3: Determining the temperature difference (ΔT); S4: Determining whether a predetermined condition is met, where the determined temperature difference (ΔT) is less than or equal to a predetermined value; S5: Changing the predetermined driving strategy such that the directional clutch (7) to be closed upon frictional engagement heats up to a temperature (T) that is less than the limit temperature (Tgrenz), if it has been determined that the predetermined condition is met; S6: Actuating the directional clutch (7) to be closed after the driving strategy has been changed in order to reverse the direction of rotation.

Description

[0001] In conventional reversing gearboxes, reversing clutches are used to change direction. These reversing clutches, also called directional clutches, are opened or closed depending on the desired direction of rotation of the gearbox's output shaft. Changing the direction of rotation of the output shaft results in a change in the direction of travel of the machine.

[0002] To change direction, the direction coupling for the current direction of travel is opened and the direction coupling for the new direction of travel is modeled as closed. Such a change of direction, or reversal of the direction of rotation, is also called a reversal.

[0003] Each reversal introduces energy into the directional clutch, causing it to heat up. During the operation of machinery, several reversals can occur in quick succession. If this happens, the directional clutches may not have enough time to cool down before being engaged again.

[0004] The temperature of the directional clutches can therefore rise to such an extent that it can lead to damage. To prevent damage, actuation of the directional clutch can be prevented if a limit temperature is exceeded. In other words, a directional clutch that is too hot can be opened and held in this state until it has cooled sufficiently. A reversal intended by the user can thus be aborted if the temperature of a directional clutch is too high. This leads to reduced machine availability and productivity losses due to unnecessary downtime.

[0005] DE 198 30 953 A1 discloses a drive train with a reversing gear for changing the direction of travel. The reversing gear has a clutch for forward travel and a clutch for reverse travel, which are actuated during reversing.

[0006] The task is to create a method and a device for reversing the direction of rotation in a drive train of a working machine, which will improve machine availability.

[0007] This problem is solved by the features of the independent patent claim. Advantageous further developments are the subject of the dependent claims.

[0008] A method for reversing the direction of rotation in the drive train of a working machine is proposed. A working machine can be, in particular, a construction machine or an agricultural machine. The drive train can include a reversing gearbox with directional clutches. The reversing gearbox can include a planetary gear set which, for example, can rotate as a single unit without loss during forward travel when a forward-travel directional clutch is engaged. When the direction of rotation is reversed to effect reverse travel, the forward-travel directional clutch is opened and the reverse-travel directional clutch is engaged. The power flow through the planetary gear set remains the same. The planetary gear set is responsible for adjusting the gear ratio.

[0009] The drivetrain can include a drive motor, for example, an internal combustion engine. The drivetrain can include a control device for automatically reversing the direction of rotation and thus the direction of travel. The control device can be configured to control individual components of the drivetrain, for example, the drive motor or the directional couplings, or multiple components of the drivetrain.

[0010] A reversal of direction refers to a change in the direction of travel of the machine. This process is also called reversing. Such a reversal, or change in direction of travel, can be initiated by the operator using a control element. In response to the activation of this element, the machine can decelerate in the original direction of travel and then accelerate again in the new direction, according to a predefined driving strategy.

[0011] Such a driving strategy can, for example, include a predetermined reduction of the clutch differential speed between a clutch input speed and a clutch output speed of the reversing clutch over time. The reduction of the clutch differential speed is defined in the given driving strategy and is achieved by engaging a reversing clutch at a predetermined time and with a predetermined pressure or clutch torque. The resulting friction reduces the clutch differential speed. This reduction of the clutch differential speed over time is therefore also referred to as friction work.

[0012] The method is suitable for use in a continuously variable power-split transmission, in a powershift transmission with a torque converter, or in a hydrostatic transmission with reversing clutches.

[0013] To reverse the direction of rotation or change the direction of travel, one of the directional couplings is opened and the other is closed. The directional couplings can be multi-plate couplings.

[0014] The method and the device are based on the understanding that by implementing targeted measures to prevent an excessive increase in the directional clutch temperature, the need for the directional clutch to be deactivated due to overheating can be avoided. In particular, the change of direction can be executed in such a way that the temperature of a clutch to be engaged does not exceed a predetermined limit temperature during frictional engagement. This prevents a situation in which a directional clutch has to be disengaged for cooling.

[0015] In this process, the energy input into the directional coupling, normally caused by the change in direction, is adjusted depending on the difference between the expected temperature of a directional coupling to be closed after frictional engagement and the specified limit temperature. The difference between the expected temperature and the limit temperature is also referred to as the temperature difference.

[0016] The energy input normally caused by a change of direction is the energy input that would occur if the change of direction were carried out using a predetermined or preset driving strategy. The preset driving strategy for changes of direction can be predefined for the machine. This preset driving strategy can always be used for changes of direction when the distance or temperature difference is sufficiently large and at least not zero. The preset driving strategy can, for example, be selected such that a change of direction results in a uniform deceleration and acceleration of the machine. Advantageously, the change of direction occurs in such a way that the machine changes direction without any jerky movements.The deceleration of the working machine in the current direction of travel and the acceleration of the working machine in the new direction of travel can be the same.

[0017] The energy input into a directional clutch during a reversal of rotation depends on the output speed of the reversing gear or the speed of the driven machine at the start of the reversal. The start of the reversal can be understood as the point in time at which the directional clutch is subjected to torque and, in a modeled fashion, closed. The higher the output speed of the reversing gear or the speed of the driven machine at the start of the clutch reversal, the greater the frictional work required by the directional clutch to achieve frictional engagement or to reduce the differential speed between the clutch and the drive. Accordingly, more heat is generated in the directional clutch when it is closed at a time when the output speed is high.

[0018] The energy input can therefore be reduced by initiating the change of direction not at a predetermined time, but at a later time. The output speed can be reduced until this later time so that when the directional clutch is closed at that later time, a correspondingly reduced energy input is required to reverse the direction of rotation. For example, if the actual temperature of the directional clutch to be closed is sufficiently high, it can only be closed when the output speed is zero, i.e., when the machine is stationary. In other words, a maximum output speed or speed of the machine can be specified for the clutch reversal to begin. With a small temperature difference, the directional clutch will only engage near standstill of the output shaft.In extreme cases, this is only permitted when the output shaft is stationary. This changes the predetermined driving strategy and reduces the energy input into the directional clutch.

[0019] The energy input into the directional clutch to be engaged during a reversal of rotation also depends on the reversing aggressiveness. Reversing aggressiveness refers to the deceleration and acceleration dynamics of the output shaft or the vehicle. Specifically, reversing aggressiveness corresponds to a reduction in rotational speed followed by an increase in rotational speed in the opposite direction per unit of time. High reversing aggressiveness is present when a large change in rotational speed occurs per unit of time. In other words, high reversing aggressiveness occurs when the gradient of the output rotational speed during reversal is high. A predetermined reversing aggressiveness can be specified by the preset driving strategy. The reversing aggressiveness can be adjusted so that it decreases as the temperature difference decreases.In other words, the reversing aggressiveness can be adjusted from a predetermined value depending on the temperature difference. Reducing the reversing aggressiveness reduces the clutch load during reversing.

[0020] The energy input into the directional coupling to be closed during a reversal of rotation also depends on the coupling differential speed or the actual speed of the drive motor if the directional coupling is connected to the drive motor on the input side. To reduce the energy input into the directional coupling to be closed, the input speed can be reduced by specifying a lower target speed for the drive motor. The differential speed at the directional couplings corresponds directly to the input speed. Therefore, a lower drive motor speed results in a lower differential speed in the directional coupling and thus less friction work or energy input into the directional coupling.

[0021] The energy input into the directional clutch being engaged during a reversal of rotation also depends on the clutch slip duration. Clutch slip duration is the time required until frictional engagement is established in the clutch. When frictional engagement is achieved, the clutch halves of the directional clutch rotate synchronously. The clutch slip duration depends on the output speed at the start of the reversal and the required reversing aggressiveness. Therefore, by adjusting the clutch slip duration from a preset value, the output speed at the start of the reversal and the reversing aggressiveness can be determined.

[0022] The energy input can be reduced in one of the ways described above or by a combination of the ways described above. In this way, the directional clutch to be closed can always be actuated, since an impermissible increase in the directional clutch temperature due to adjustment of the driving strategy is avoided.

[0023] In the procedure described above, the first step involves determining the actual temperature of the directional coupling to be closed. Determining the actual temperature can be done by calculating or estimating it, or by measuring it.

[0024] In a further step, the expected temperature of the directional clutch to be engaged can be determined. This expected temperature can be calculated based on the measured actual temperature and a predicted temperature increase due to a predetermined driving strategy during the reversal of rotation. As mentioned above, a driving strategy can be predefined. In other words, a general or standard driving strategy can be specified, from which deviations are made as needed.

[0025] In a further step, the temperature difference between the expected temperature and the limit temperature can be determined.

[0026] In a further step, it can be determined whether a predetermined condition is met, where the measured temperature difference is less than or equal to a predetermined value. The predetermined value can, for example, be zero. If the predetermined value is zero, the predetermined condition is met if the expected temperature corresponds to the limit temperature. A value less than zero indicates that the expected temperature exceeds the limit temperature.

[0027] In a further step, if the predetermined condition is met, the predetermined or preset driving strategy can be modified so that the directional clutch to be closed heats up to a temperature lower than the limit temperature when frictionally engaged. The driving strategy is modified by changing the factors or parameters described above that influence the energy input.

[0028] In a further step, the directional clutch to be closed is engaged after the driving strategy has been changed, in order to reverse the direction of rotation. Changing the driving strategy can noticeably alter the behavior of the machine for the operator during a change of direction. For example, the change of direction may be slower overall.

[0029] Preferred embodiments of the invention are explained below with reference to the accompanying drawings. Fig. Figure 1 shows temperature profiles of direction-of-travel couplings during successive changes of direction of rotation. Fig. Figure 2 shows a time course of an output speed of a reversing gear and a change in the entry time into a reversing. Fig. Figure 3 shows a reduction in the rotational speed of a drive machine. Fig. 4 shows a reduction in reversal aggressiveness. Fig. Figure 5 shows a reduction in clutch slip time. Fig. Figure 6 shows process steps according to one embodiment. Fig. Figure 7 shows a schematic representation of a drive train with a control unit according to one embodiment.

[0030] The procedure is described below with reference to a powertrain. 1 a machine described. The drive train 1 is in Fig. 7 schematically represented and shows a drive machine 2 and a gearbox 5 up. The gearbox 5 features a reversing gear 3 with two directional couplings 6 and 7 Furthermore, a control unit is required. 4 provided which is connected to the drive machine 2 and the gearbox 5 is connected in order to control them.

[0031] In Fig. Figure 1 shows the temperature profile of the directional couplings. 6and 7 shown in several successive reversals. The reversal times t1 until t6 are shown in a separate diagram below the temperature curve.

[0032] Each directional coupling 6 , 7 When activated, this results in an energy input, which manifests itself as a temperature increase. At a certain point in time t1 In the illustration shown, the directional coupling 7 closed. This results in the temperature of the directional clutch 7 after the time t1 It initially rises sharply to a maximum value. The maximum value corresponds to the temperature. T The directional clutch experiences a significant temperature increase during frictional engagement. This results from the frictional work required within the clutch to achieve frictional engagement. The directional clutch 7 will then be up to a certain point t2It is kept closed. After reaching the maximum value, the temperature of the directional clutch drops. 7 depending on the cooling capacity of the clutch. At the time t2 The directional coupling will 7 opened and the directional clutch 6 Closed. The directional coupling 7 It can now cool down faster, which is why the temperature of the directional clutch 7 from that point on t2 drops more quickly. The temperature profile of the directional clutch 6 between the time t2 and a time t3 , in which a reversal takes place, behaves similarly to the temperature profile of the directional clutch 7 between the points in time t1 and t2 As in Fig. As shown in 1, the directional clutch is reached. 7 until the time t3 not their original starting temperature T a Rather, the directional clutch cools down.7 only to an actual temperature higher than the initial temperature Ta T ist away.

[0033] The temperature of the directional couplings must not exceed a specified limit temperature. T grenz not exceed. According to the embodiment, therefore, the value in is exceeded at each reversal. Fig. The 6 methods shown for a directional coupling to be closed were carried out.

[0034] In Fig. 6 is a method for reversing the direction of rotation in a drive train 1 a working machine according to the embodiment described. In the method, in a first step S1 the current temperature T ist the directional coupling to be closed 7 determined. In the illustrated embodiment, this actual temperature is the temperature of the directional coupling. 7 at the time t3 .

[0035] In step S2 is based on the determined actual temperature T ist an expected temperature T erw the directional clutch 7 Determined during frictional engagement. A predicted temperature increase is used in this process. T erh assuming that would occur if the directional clutch 7 is activated without changing a driving strategy.

[0036] In step S3 will there be a temperature difference ΔT between the limit temperature T grenz and the expected temperature T erw determined.

[0037] In step S4 It is determined whether the temperature difference ΔT zero or less than a minimum distance to the limiting temperature. In the present embodiment, the expected temperature is T erw between the points in time t3 and t4 below the limit temperature T grenz Therefore, the process is aborted at this point and the directional coupling is closed without changing the driving strategy. At the time t5 will this in Fig. The six procedures shown were repeated. The steps S1 until S4 will be carried out as already described. However, in step S4 now established that the temperature difference ΔT is less than zero, since the expected temperature T erw the limit temperature T grenz exceeds the limit. The predetermined condition is therefore met. Therefore, in step 1... S5 The driving strategy has now been changed so that the directional clutch reaches the expected temperature. T erw not reached or settled at a temperature T heated, which are smaller than those after the time t5 expected temperature with unchanged driving strategy.

[0038] Following this, in step S6 the directional clutch 7After the driving strategy has been changed, the directional clutch is activated to reverse the direction of rotation. This causes the directional clutch to heat up. 7 only one temperature T , which fall below the limit temperature T grenz lies. A changed temperature profile is in Fig. 1 shown as a dashed line.

[0039] The energy input into, or the heating of, the directional clutch depends on the driving strategy during the reversal of rotation. Fig. 2 to Fig. Figure 5 shows embodiments with measures to reduce the energy input into the directional coupling.

[0040] In Fig. Figure 2 shows a predetermined time profile of the output speed na of the reversing gear during reversal. Above the time axis, the output speed in the current direction of rotation is shown, and below the time axis, the output speed in the new direction of rotation is shown. The gradient of the output speed is fixed in this embodiment and should not be changed. To reduce the energy input into the clutch, the directional clutch is not engaged at time . t5 closed, but only with a time delay at the time t 51 , since at the time t 51 already a lower output speed n soll is available.

[0041] In Fig. Figure 3 shows a further measure to reduce energy input. This involves increasing the rotational speed. n an the drive motor 2 and thus the input speed n e the reversing coupling is reduced.

[0042] In Fig. Figure 4 shows a further measure to reduce energy input. More precisely, it shows Fig. 4. Adjusting the reversing aggressiveness to reduce energy input. This involves adjusting the gradient of the output rotational speed. n a reduced, thereby reducing energy input.

[0043] In Fig. Figure 5 shows a further measure to reduce energy input. This involves reducing the clutch slippage time. t r reduced to result in less energy input into the directional clutch.

[0044] After a change in energy input by one or more of the elements in the Fig. 2 to Fig. The measures described in step 5 are described below. S6 executed to engage the directional coupling 7 to close. The procedure is repeated analogously for the directional coupling during each reversal. 6 This is carried out when it is to be closed. Reference symbol list 1 Powertrain 2 Drive machine 3 reversing gears 4 Control unit 5 gearboxes 6 directional coupling 7 directional coupling t1...t6 Reversal times t 51 time T ist Actual temperature of the directional coupling to be closed Terw expected temperature of the directional coupling to be closed T grenz Limit temperature T erh Temperature increase Temperature after frictional engagement ΔT temperature difference n a Output speed of the reversing gearbox n soll Target output speed n e Input speed of the reversing gearbox n an Speed ​​of the drive machine t r Clutch slippage time QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 19830953 A1

[0005]

Claims

[1] Method for reversing the direction of rotation in a drive train (1) of a working machine, wherein the drive train has a reversing gear (3) with directional couplings (6, 7), wherein to reverse the direction of rotation one of the directional couplings (6) is opened and the other directional coupling (7) is closed, characterized by , that depending on a temperature difference (ΔT) between an expected temperature (T erw ) of the directional coupling (7) to be closed at frictional engagement and a predetermined limit temperature (T grenz ) an energy input into the directional coupling (7) to be closed is controlled by the change of direction in such a way that the temperature (T) of the directional coupling to be closed does not exceed the limit temperature (T grenz does not exceed. [2] Method according to claim 1, characterized by the steps S1: Determining the current temperature (T ist ) the directional coupling to be closed (7), S2: Determining the expected temperature (T erw ) of the directional coupling (7) to be closed during frictional engagement based on the determined actual temperature (T ist ) and a predicted temperature increase (T erh ) due to a predetermined driving strategy during the reversal of the direction of rotation, S3: Determining the temperature difference (ΔT), S4: Determine whether a predetermined condition is met, where the measured temperature difference (ΔT) is less than or equal to a predetermined value. S5: Changing the predetermined driving strategy such that the directional clutch (7) to be closed heats up to a temperature (T) during frictional engagement that is lower than the limit temperature (T grenz ) is when it has been determined that the predetermined condition is met, S6: Actuating the directional clutch (7) to be closed after changing the driving strategy in order to reverse the direction of rotation. [3] Method according to claim 2, characterized by , that the driving strategy includes operation of the drive train and / or actuation of the directional clutch (7) to be closed. [4] Method according to claim 3, characterized by , that changing the driving strategy results in a reduction of an initial speed (n a ) of the gearbox. [5] Method according to claim 4, wherein the directional clutch (7) to be closed is only actuated when the output speed (n a ) to a target output speed (n soll ) was reduced. [6] Method according to any one of claims 3 to 5, characterized by , that changing the operation of the drive train results in a reduction of an input speed (n e ) of the gearbox. [7] Method according to claim 6, wherein the drive train (1) comprises a drive machine (2) and for reducing the input speed (n e ) a rotational speed (n an) of the drive machine (2) is reduced. [8] Method according to any one of claims 3 to 7, characterized by , that changing the actuation of the directional clutch (7) to be closed includes a reduction of reversing aggressiveness. [9] Method according to claim 8, wherein to reduce the reversing aggressiveness a gradient of an output rotational speed (n a ) of the gearbox is reduced. [10] Method according to any one of claims 3 to 9, characterized by , that changing the actuation of the directional clutch to be closed reduces the clutch slip time (t r ) includes. [11] Method according to any one of claims 2 to 10, characterized by , that the predetermined value is zero. [12] Method according to any one of the preceding claims, characterized by , that when determining the expected temperature (T erw ) a cooling rate of the directional coupling (7) to be closed is taken into account. [13] Control device (4) configured to perform the procedure according to any one of the preceding claims.